1. Field of the Invention
The present invention relates to Mobile IP network technology. More particularly, the present invention relates to Mobile IP dynamic home address assignment.
2. Description of the Related Art
Mobile IP is a protocol which allows laptop computers or other mobile computer units (referred to as xe2x80x9cMobile Nodesxe2x80x9d herein) to roam between various sub-networks at various locationsxe2x80x94while maintaining internet and/or WAN connectivity. Without Mobile IP or related protocol, a Mobile Node would be unable to stay connected while roaming through various sub-networks. This is because the IP address required for any node to communicate over the internet is location specific. Each IP address has a field that specifies the particular sub-network on which the node resides. If a user desires to take a computer which is normally attached to one node and roam with it so that it passes through different sub-networks, it cannot use its home base IP address. As a result, a business person traveling across the country cannot merely roam with his or her computer across geographically disparate network segments or wireless nodes while remaining connected over the internet. This is not an acceptable state-of-affairs in the age of portable computational devices.
To address this problem, the Mobile IP protocol has been developed and implemented. An implementation of Mobile IP is described in RFC 2002 of the Network Working Group, C. Perkins, Ed., October 1996. Mobile IP is also described in the text xe2x80x9cMobile IP Unpluggedxe2x80x9d by J. Solomon, Prentice Hall. Both of these references are incorporated herein by reference in their entireties and for all purposes.
The Mobile IP process and environment are illustrated in FIG. 1. As shown there, a Mobile IP environment 2 includes the internet (or a WAN) 4 over which a Mobile Node 6 can communicate remotely via mediation by a Home Agent 8 and a Foreign Agent 10. Typically, the Home Agent and Foreign Agent are routers or other network connection devices performing appropriate Mobile IP functions as implemented by software, hardware, and/or firmware. A particular Mobile Node (e.g., a laptop computer) plugged into its home network segment connects with the internet through its designated Home Agent. When the Mobile Node roams, it communicates via the internet through an available Foreign Agent. Presumably, there are many Foreign Agents available at geographically disparate locations to allow wide spread internet connection via the Mobile IP protocol. Note that it is also possible for the Mobile Node to register directly with its Home Agent.
As shown in FIG. 1, Mobile Node 6 normally resides on (or is xe2x80x9cbased atxe2x80x9d) a network segment 12 which allows its network entities to communicate over the internet 4 through Home Agent 8 (an appropriately configured router denoted R2). Note that Home Agent 8 need not directly connect to the internet. For example, as shown in FIG. 1, it may be connected through another router (a router R1 in this case). Router R1 may, in turn, connect one or more other routers (e.g., a router R3) with the internet.
Now, suppose that Mobile Node 6 is removed from its home base network segment 12 and roams to a remote network segment 14. Network segment 14 may include various other nodes such as a PC 16. The nodes on network segment 14 communicate with the internet through a router which doubles as Foreign Agent 10.
Mobile Node 6 may identify Foreign Agent 10 through various solicitations and advertisements which form part of the Mobile IP protocol. When Mobile Node 6 engages with network segment 14, Foreign Agent 10 relays a registration request to Home Agent 8 (as indicated by the dotted line xe2x80x9cRegistrationxe2x80x9d). The Home and Foreign Agents may then negotiate the conditions of the Mobile Node""s attachment to Foreign Agent 10. For example, the attachment may be limited to a period of time, such as two hours. When the negotiation is successfully completed, Home Agent 8 updates an internal xe2x80x9cmobility binding tablexe2x80x9d which specifies the care-of address (e.g., a collocated care-of address or the Foreign Agent""s IP address) in association with the identity of Mobile Node 6. Further, the Foreign Agent 10 updates an internal xe2x80x9cvisitor tablexe2x80x9d which specifies the Mobile Node address, Home Agent address, etc. In effect, the Mobile Node""s home base IP address (associated with segment 12) has been shifted to the Foreign Agent""s IP address (associated with segment 14).
Now, suppose that Mobile Node 6 wishes to send a message to a corresponding node 18 from its new location. An output message from the Mobile Node is then packetized and forwarded through Foreign Agent 10 over the internet 4 and to corresponding node 18 (as indicated by the dotted line xe2x80x9cpacket from MNxe2x80x9d) according to a standard internet protocol. If corresponding node 18 wishes to send a message to Mobile Nodexe2x80x94whether in reply to a message from the Mobile Node or for any other reasonxe2x80x94it addresses that message to the IP address of Mobile Node 6 on sub-network 12. The packets of that message are then forwarded over the internet 4 and to router R1 and ultimately to Home Agent 8 as indicated by the dotted line (xe2x80x9cpacket to MN(1)xe2x80x9d). From its mobility binding table, Home Agent 8 recognizes that Mobile Node 6 is no longer attached to network segment 12. It then encapsulates the packets from corresponding node 18 (which are addressed to Mobile Node 6 on network segment 12) according to a Mobile IP protocol and forwards these encapsulated packets to a xe2x80x9ccare ofxe2x80x9d address for Mobile Node 6 as shown by the dotted line (xe2x80x9cpacket to MN(2)xe2x80x9d). The care-of address may be, for example, the IP address of Foreign Agent 10. Foreign Agent 10 then strips the encapsulation and forwards the message to Mobile Node 6 on sub-network 14. The packet forwarding mechanism implemented by the Home and Foreign Agents is often referred to as xe2x80x9ctunneling.xe2x80x9d
In today""s rapidly expanding economy, many businesses are increasing their work force considerably. With this expansion, these businesses may wish to provide most or all of these employees with access to the internet. At the same time, such businesses typically have a limited number of IP addresses for use by these employees. Therefore, it may be impossible to permanently assign an IP address to some or all of the mobile nodes used by these employees.
Although a business may not be able to permanently assign a unique IP address to each mobile node, each mobile node roaming to a Foreign Agent must be able to receive packets from corresponding nodes. As described above, the mobile node""s IP address (i.e., Home Address) is typically used to identify the mobile node. Thus, when messages are sent to a mobile node, they are sent to that mobile node""s IP address. In view of the above, it would be desirable if an IP address could be assigned temporarily to a mobile node on an as-needed basis.
The present invention provides methods and apparatus for assigning an IP address to a mobile node during registration. This may be accomplished by mapping a mobile node ID associated with the mobile node to the assigned IP address. In this manner, the mobile node may be properly identified during registration and the mobile node may use the assigned IP address upon completion of registration.
According to one aspect of the invention, a method of sending a registration request in a mobile node is provided. A mobile node ID associated with the mobile node is obtained. A registration request packet is then composed. The registration request packet stores at least a portion of the mobile node ID in the registration request packet. The registration request packet is then sent to a Home Agent associated with the mobile node.
According to another aspect of the invention, a method of processing a registration request packet received by a Home Agent from a mobile node is provided. The registration request packet is received from a mobile node. It is then ascertained whether the mobile node designated by the registration request packet needs an IP address. An IP address is then assigned to the mobile node if it is ascertained that the mobile node needs an IP address. A registration reply specifying the IP address assigned to the mobile node is then composed.
According to yet another aspect of the invention, a method of processing a registration reply packet received by a Foreign Agent from a Home Agent is disclosed. The registration reply packet is received from the Home Agent. The registration reply packet specifies at least a portion of a mobile node ID and an IP address associated with a mobile node. The portion of the mobile node ID and the IP address are then obtained from the registration reply packet. A visitor table is then updated with a mapping of the mobile node ID to the IP address associated with the mobile node. The registration reply packet is then sent to the mobile node.
The present invention may be used to temporarily assign an IP address to a mobile node on an as-needed basis. In this manner, a pool of IP addresses may be advantageously distributed to preserve the pool of IP addresses. Accordingly, the present invention permits an entity to economically utilize a limited number of IP addresses.